Method and apparatus for cracking and rectifying petroleum oils and the like



J. M. WADSWORTH Nov. 20, 1928.,

Patented Nov.` 20, 1928.

UNITED STATES. PATENT OFFICE. f l

JAMES M. wAnswoRvrH, OFSAND SPRINGS, oxLAHoMA.

METHOD AND APPARATUS FOR CRACKING AND RECTIEYING PETROLEUM OILS ANDV THE LIKE.

Application filed March 12, v15,26. Serial No. 94,288.

This invention relates to a novel method and apparatus for cracking and rectifying petroleum oils and the like.

The majority of stills employed for cracking high boiling point hydrocarbons into low boiling point hydrocarbons now operate with the heating element and reaction chamber under considerable pressure. In many Aof the processes, it is the practice to relieve this pressure down to about three atmospheres and condense and rectify the products under this low pressure, which results in rendering rectification exceedingly ditlicult and necessitates an auxiliary gasoline plant of the absorption or compressor Itype to recover the gasoline carried away in the uncondensed gases relieved from the system. The gasoline made in the system under this low pressure is an unstable product due to its content of dissolved uncondensible gases. It is impossible to properly rectify the vapor from such a process under this low pressure without resortingto artificial cooling, at the top of the rectifying column. Processes in use which do not reduce the pressure before condensing make no effort to untilize this pressure to rectify the vapor and separate its gasoline content from the uncondensible gas.

Any hydrocarbon liquid at a given temperature exerts a certain vapor pressure# As this temperature is increased, the vapor pressure increases until it is suiiicient to overcome the pressure above the liquid, when boiling will occur and the more volatile fractions be driven ofi'.

The primary object of my inventionis. to utilize the existent pressure of the bsystem to accomplish rectification'of the ylighter hydrocarbon components produced in cracking, such as the separation of pressure still gaso- 'line from the socalled non-condensible gases. In this -cracking operation, my method is based upon the fact that the problem involved is one of properly separating four compo; nents of a hydrocarbon mixture, for instance,

1, residual fluxg2, recycle stock; 3, cracked gasoline; and 4, uncondensed-gases. So far as I am aware, none of the present tube and tank crackingstillsor shell stills recognizethe existence of the fourth component or pro?. vide rectifying means for separating the third and fourth components. For this reason tht` f crackedgasoline produced by themcont'ains Vcompression plant.

a considerable amount of these uncondensed gases in dissolved form, and as a result', excessive losses are experienced in handling the commodity. In addition the uncondensed gases leaving the cracked gasoline condenser 1n mostl plants, contain a very considerable proportion of gasolinewhich can only be recovered through an efficientl absorption or My improved method utilizes the pressure' already existent and available to accomplish the desired fractionationv and results in a very marked saving over present mea-ns, and produces increased yields.

Referring again to the prior art, it maybe stated that in the operation of any tube or tank pressure system now commercially used, the method pursued is to operate these plants under considerablepressure and temperature for the purpose of destroying the molecular arrangements of the hydrocarbons to eHect new groupings, so as to change a portion of the charged stock into hydrocarbons` of lower boiling point. Having produced these lower boiling point hydrocarbons, it is desirable to rectify them into their respective components, and as before stated, in doing this I utilize the pressure and temperature already existent in the cracking plant to conductthe rectification of the lower boiling point hydrocarbons formed during cracking, and I carry out this rectication under saidpressure. or at a reduced pressure and temperature from that existing in the crackin unit. If the pressure and temperature emp oyed during the cracking is not used for rectification, the products cannot be completely obtained without resorting to artificial cooling at the head of the rectifying column. y

Each component of anyhydrocarbon'series' has a certain vapor pressure for any given, temperature and below a certain critical temperature and pressure exists inthe liquid phase; above this ,critical temperature and pressure it will exist only inthe vapor phase. It is? desirable then to conduct the rectifica- .tion at a temperature and pressure such that the'4 desirable components willv exist iinjthe 100 vrliquid phase and the undesirable components e through a pipe 6. The oil to accomplish sharp rectification of the components of the liquid.

While I have set forth some of the objects of the present invention, other objects will appear as this description roceeds, and in reading the present description, reference should be had to the accompanying drawing.

The drawing is a diagrammatic view of an apparatus ,which I have devised for carrying out theimproved process.

The oil to be subjected to cracking, enters the system by Way of the pipe 1, and is forced by a pump 2, through a pipe 3, and a heat exchanger 4, the latter being heated by the vapors leaving a fractionation tower 5, after passing through the heat exchanger, flows through a pipe 7 and then through a second heat exchanger 8, the latter being heated by the residuum discharged from the column 5, through a pipe 9. The oil thus preheated flows through a pipe l() into a high pressure pump 11 which forces the same under considerable pressure through a heating coil 12, where it is heated to a cracking temperature. The heating coil discharges'the oil into a reaction chamber 13 of the ordinary type. -A suitable pressure regulating valve 14 is attached to the outlet pipe 15 of the reaction chamber, so that vapor and oil ea`n be released from sa1d chamber at any lower pressure desired. This mixture of vapor and oil enters the stripping column 5 about midway.

between the to and bottom of the same, and the residuum eaves at the bottom through the pipe 9 and enters the heat exchanger 8, Where it functions to preheat the charging stock. From the heat exchanger. the residuum flows through a pipe 16 to storage. 'In the column 5, the gasoline and otherl vapors are separated from the residuum, and these vapors pass olf through the heat exchanger 4 y way of pipe 6. This heat exchanger may, if desired, function as a reiiux conv denser, so that condensate resulting from the vapors may be returned to the top of the column 5 to cool the topof the column and provide the necessary reflux liquid for rectification. Vapors passing through the heat exchanger 4 are conducted by a pipe 17 to the central lportion of a second rectifying column 18, which is equipped with a refiux condenser 19, to which the lightest vapors How by way of pipe 20. All condensate is reiluxed from thisj condenser through pipe 21 intoA the upper portion of the rectifying column,

while the uncondensed gas passes out through a pressure regulating valve 22 into a pipe 23.

The pressure may be released by permitting the same to operate an expansion engine 24, preferably the prime mover of the process itself, for the purpose of securing the work out of this expansion. Further, the cold created by the expansion of the dry gas may be employedto refrigerate a cooling medium in the cooler 25, vand this refrigerating medium may be employed to condense the products yielded fromthe process. t

In the first rectifying column 5,` above the stripping portion of the same, a recycle stock may be drawn from one of the lower trays and may be fed through a pipe 26 into a ioat pot 27 which controls the passage of this recycle stock to a pipe 28 that conveys the sameto a coil 29 arranged in the lower portion of thefrectifying column 18. Hence, this recycle stock may be used as a heating medium for the second rectif ing column. TheA coil 29 has regulating va ves 30 and 31, and a b -pass pipe 32is provided for the purpose of y-passing some of the recycle stock past the coil 29. The by-pass has a control valve 33, and the recycle stock is nally discharged through a pipe 34. The. rectified gasoline at the lower portion of the column 18 is utilized to control a float valve 35, which regulates the flow of the finished gasoline through the discharge pipe 36.

A valve 38 in the pipe 9 at the lower portion of the column 5 is provided with a float 37, actuated by the residuum at the bottom of the tower 5. y L

In practicing my process, the incoming oil is cracked and the cracked vapors and oil are fed by the pipe 15 into the tower 5, the upper portion of which is a rectifier and the lower portion of which is a'stripping still. In the column 5, the cracked vapors will rise while the oil will have a tendency to pass downward. Due to this counter current contact of vapors and oil the gasoline and other vapors will be sharply separated from the residuum, and vthese vapors will finally enter the column 18. As this column has a heating means at its lower end and a cooling in sharp separation of the lighter gases from r the gasoline vapors. Consequently all the components which it is desired to incorporate in the finished gasoline will gather at the bottom of the tower 18, and be discharged through the pipe 36, while the lighter components of the mixture which it is desired to eliminate from the ygasoline will be discharged from. the system by way of pipe 23. As the column 18 has a pressure control valve 22 at its gas outlet, and a float control valve 35 at its liquid outlet, it is obvious that the column 18 will Work under pressure, and consequently the vapor tension of the material undergoing treatment may be utilized to build up a predetermined pressure within the columns 5 and 18. Therefore, I am enabled by my process and apparat-us to utilize the pressure and temperature existent for the cracking operation, to'rectify the gaso- The recycle stock afterleaving libe reboiler lll).

so.l

' and at temperatures line hydrocarbons,

the details of the method and apparatus Inay be varied without departing from the basic ideas which I have outlined above and which I will hereinafter claim.

What I claim and desire to secure by Letters Patent is 1. In a method of treating petroleum oils, cracking the oil under heat and pressure to produce a mixture of gasoline hydrocarbons, hydrocarbons lighter and heavier than gasoline hydrocarbons, and residuum, rectif'ying said mixture to sharply separate the gasoline hydrocarbons and lighter hydrocarbons from heavier hydrocarbons and residuum, subsefi quently rectifying said gasoline hydrocarbons and lighter hydrocarbons, and separately withdrawing from the second rectification step, rectified liquid gasoline and uncondensed gases, and utilizing during the rectification steps, the pressure resulting from the cracking step to effect the second rectification at super-atmospheric pressure and at temperatures from substantially atmospheric upwardly. i

2. In a method of treating petroleum oils, cracking the oil under heat and pressure to produce amixture of gasoline hydrocarbons, hydrocarbons lighter and heavier than gasoline hydrocarbons and residuum, rectifying said mixture and thus sharply separating the gasoline hydrocarbons and lighter hydrocarons from heavier hydrocarbons and residuum, subsequently rectifying, said gasoline hydrocarbons and lighter hydrocarbons, and separately withdrawing from the second rectification step, rectified liquid gasoline and uncondensed gases, and utilizing the heat and pressure resulting from the vcracking ste-p during the rectification steps, to effect both rectifications at super-atmospheric `pressure from substantially atmospheric upwardly.

.3. In a method of treating cracking the oil under heat produce a mixture of hydrocarbons lighter petroleum oils, and pressure to gasoline hydrocarbons, and heavier than gasoand residuum, rectifying said mixture and thus sharply separating the gasoline hydrocarbons and lighter hydrocarbons from heavier uum, subsequently rectifying said gasoline hydrocarbons and lighter hydrocarbons alone, and separately withdrawing,` from the second rectification step, rectified liquid gasoline and uncondensed gases, utilizing, during the rectification steps` the heat andpressure resulting from the cracking step to effect hydrocarbons and residthe rectification steps at super-atmospheric pressure and at temperatures from substantially atmosphericv upwardly, and passing heavier hydrocarbons from the first rectification step through the second rectification step and out of contact with the liquid therein to furnish the heat used in the second rectificationl step. I

4. In a` method of treating petroleum oils, cracking the oil under heat and pressure to produce a mixture of gasoline hydrocarbons, hydrocarbons lighter and heavier than gasoline hydrocarbons and residuum, rectifying said mixture and sharply separating the gasoline hydrocarbons and lighter hydrocarbonsv from heavier hydrocarbons and` residuum, subsequently rectifying said gasoline hydrocarbons and lighter hydrocarbons rately withdrawing from the second rectification step, rectified liquid gasoline and uncondensed gases, utilizing, during the rectication steps, pressure from the cracking step, to effect the rectification steps at superatmospheric pressure and at temperatures from substantially atmospheric upwardly, and utilizing between the first and second rectification steps,f the heat from the residuum and said gasoline hydrocarbons and lighter hydrocarbons to preheat charging stock.

5. The process of treating hydrocarbon oil, consisting in subjecting the oil to a cracking temperature and pressure, releasing the hydrocarbons from the cracking (sphere while lowering'the pressure on the released hydrocarbons slightly but `not below super-atmospheric, sharply separate gasoline hydrocarbons and lighter hydrocarbons from heavier hydro.- carbons and residuum, withdrawing the gasoline hydrocarbons and lighter hydrocarbons and separectifying said hydrocarbons to` dition resulting from the cracking step, separately withdrawing the residuum-from the rectification step, also inthe heated condition resulting from the cracking step, utilizing said gasoline hydrocarbons, lighter hydrocarbons and residuum to preheat charging stock, subsequently rectifying said gasoline hydrocarbons and lighter hydrocarbons under super-atmospheric pressure derived from the cracking step, to split the same into stable gasoline and uncondensed gases, separately withdrawing from the Second rectification step, rectified liquid gasoline and uncondensed gases, and utilizing heavier hydrocarbons in heated condition from the first rectification step to furnish the heat employed in the second rectification step.

An apparatus for treating hydrocarbon oils, comprlsing an inlet pipe provided with a plurality of heat exchangers and a lurality of pumps, one of said pumps being a apted to raise the pressure of the oil above that of the lother pump.` a cracking unit connected to said inlet pipe,

for feeding hydrocarbons from the cracking unit into an intermediate portion of said column, means for feeding residuum liquid from the lower portion of said column 5 through one of said heat exchangers, a secmeans for feedingn ond rectifyingcolumn, light hydrocarbons from the top of the irst rectiylng column, through the other one of said heat exchangers and into an intermediate portion of the second column, a heating element arranged in the lower portion of the second column, means for feeding a part of the material undergoing treatment from the reflux condenser at the upper portion of the 4second column, a gasoline outlet at the lower ortion of the second column, a dry -gas outet'from said reflux condenser, and a ressure regulating valve in the last mentione column to permit the v'ap'or'pressure of the material undergoing treatment to exert sufficient pressure inthe columns to carry out rectication without the use of relatively low temperature cooling mediums.

In testimony whereof I aliix my signature.

JALIES M. WADSWORTH. 

